Martin Rees is a cosmologist and space scientist. He is based in Cambridge, where he has been Director of the Institute of Astronomy, a Research Professor, and, until recently, Master of Trinity College. He was President of the Royal Society during 2005–2010, and in 2005 was appointed to the House of Lords. He lectures, writes and broadcasts widely for general audiences. His books include Before the Beginning, Our Final Century?, Just Six Numbers, Our Cosmic Habitat, Gravity’s Fatal Attraction, and From Here to Infinity: Scientific Horizons, an expanded version of his BBC Reith Lectures. Ever since Our Final Century? was published, he has been concerned with the threats stemming from humanity’s ever-heavier ‘footprint’ on the global environment, and with the runaway consequences of ever more powerful technologies. These concerns led him to join with colleagues in setting up a Centre for the Study of Existential Risks (CSER). This is based in Cambridge and has a strong international advisory board.